Various exhaust after-treatment devices have been developed to effectively limit exhaust emissions from internal combustion engines. An after-treatment system for a modern diesel engine exhaust typically incorporates a diesel particulate filter (DPF) for collecting and disposing of the sooty particulate matter emitted by the diesel engine prior to the exhaust gas being discharged to the atmosphere.
Generally, a DPF acts as a trap for removing the particulate matter from the exhaust stream. A typical DPF contains precious metals, such as platinum and/or palladium, which serve as catalysts to further oxidize soot and hydrocarbons present in the exhaust stream. The DPF may be regenerated or cleaned using superheated exhaust gas to burn off the collected particulate. Efficiency of the DPF is typically assessed via a particulate matter sensor configured to detect an amount of particulate matter that managed to pass through the DPF.